'\" t
.TH "SD_EVENT_SOURCE_SET_ENABLED" "3" "" "systemd 249" "sd_event_source_set_enabled"
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.SH "NAME"
sd_event_source_set_enabled, sd_event_source_get_enabled, SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT \- Enable or disable event sources
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-event\&.h>
.fi
.ft
.sp
.ft B
.nf
enum {
        \fBSD_EVENT_OFF\fR = 0,
        \fBSD_EVENT_ON\fR = 1,
        \fBSD_EVENT_ONESHOT\fR = \-1,
};
.fi
.ft
.HP \w'int\ sd_event_source_set_enabled('u
.BI "int sd_event_source_set_enabled(sd_event_source\ *" "source" ", int\ " "enabled" ");"
.HP \w'int\ sd_event_source_get_enabled('u
.BI "int sd_event_source_get_enabled(sd_event_source\ *" "source" ", int\ *" "enabled" ");"
.SH "DESCRIPTION"
.PP
\fBsd_event_source_set_enabled()\fR
may be used to enable or disable the event source object specified as
\fIsource\fR\&. The
\fIenabled\fR
parameter takes one of
\fBSD_EVENT_ON\fR
(to enable),
\fBSD_EVENT_OFF\fR
(to disable) or
\fBSD_EVENT_ONESHOT\fR\&. If invoked with
\fBSD_EVENT_ONESHOT\fR
the event source will be enabled but automatically reset to
\fBSD_EVENT_OFF\fR
after the event source was dispatched once\&.
.PP
Event sources that are disabled will not result in event loop wakeups and will not be dispatched, until they are enabled again\&.
.PP
\fBsd_event_source_get_enabled()\fR
may be used to query whether the event source object
\fIsource\fR
is currently enabled or not\&. It returns the enablement state (one of
\fBSD_EVENT_ON\fR,
\fBSD_EVENT_OFF\fR,
\fBSD_EVENT_ONESHOT\fR) in
\fIenabled\fR, if it is not
\fBNULL\fR\&. It also returns true if the event source is not disabled\&.
.PP
Event source objects are enabled when they are first created with calls such as
\fBsd_event_add_io\fR(3),
\fBsd_event_add_time\fR(3)\&. However, depending on the event source type they are enabled continuously (\fBSD_EVENT_ON\fR) or only for a single invocation of the event source handler (\fBSD_EVENT_ONESHOT\fR)\&. For details see the respective manual pages\&.
.PP
As event source objects stay active and may be dispatched as long as there is at least one reference to them, in many cases it is a good idea to combine a call to
\fBsd_event_source_unref\fR(3)
with a prior call to
\fBsd_event_source_set_enabled()\fR
with
\fBSD_EVENT_OFF\fR, to ensure the event source is not dispatched again until all other remaining references are dropped\&.
.SH "RETURN VALUE"
.PP
On success,
\fBsd_event_source_set_enabled()\fR
returns a non\-negative integer\&.
\fBsd_event_source_get_enabled()\fR
returns zero if the source is disabled (\fBSD_EVENT_OFF\fR) and a positive integer otherwise\&. On failure, they return a negative errno\-style error code\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EINVAL\fR
.RS 4
\fIsource\fR
is not a valid pointer to an
sd_event_source
object\&.
.RE
.PP
\fB\-ENOMEM\fR
.RS 4
Not enough memory\&.
.RE
.PP
\fB\-ECHILD\fR
.RS 4
The event loop has been created in a different process\&.
.RE
.SH "NOTES"
.PP
These APIs are implemented as a shared library, which can be compiled and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.SH "SEE ALSO"
.PP
\fBsd-event\fR(3),
\fBsd_event_add_io\fR(3),
\fBsd_event_add_time\fR(3),
\fBsd_event_add_signal\fR(3),
\fBsd_event_add_child\fR(3),
\fBsd_event_add_inotify\fR(3),
\fBsd_event_add_defer\fR(3),
\fBsd_event_source_unref\fR(3),
\fBsd_event_source_set_ratelimit\fR(3)
